Dopheide Andrew, Lear Gavin, Stott Rebecca, Lewis Gillian
School of Biological Sciences, University of Auckland, Auckland, New Zealand.
Appl Environ Microbiol. 2009 Aug;75(16):5261-72. doi: 10.1128/AEM.00412-09. Epub 2009 Jun 26.
Ciliates are an important component of aquatic ecosystems, acting as predators of bacteria and protozoa and providing nutrition for organisms at higher trophic levels. Understanding of the diversity and ecological role of ciliates in stream biofilms is limited, however. Ciliate diversity in biofilm samples from four streams subject to different impacts by human activity was assessed using microscopy and terminal restriction fragment length polymorphism (T-RFLP) analysis of 18S rRNA sequences. Analysis of 3' and 5' terminal fragments yielded very similar estimates of ciliate diversity. The diversity detected using microscopy was consistently lower than that suggested by T-RFLP analysis, indicating the existence of genetic diversity not apparent by morphological examination. Microscopy and T-RFLP analyses revealed similar relative trends in diversity between different streams, with the lowest level of biofilm-associated ciliate diversity found in samples from the least-impacted stream and the highest diversity in samples from moderately to highly impacted streams. Multivariate analysis provided evidence of significantly different ciliate communities in biofilm samples from different streams and seasons, particularly between a highly degraded urban stream and less impacted streams. Microscopy and T-RFLP data both suggested the existence of widely distributed, resilient biofilm-associated ciliates as well as ciliate taxa restricted to sites with particular environmental conditions, with cosmopolitan taxa being more abundant than those with restricted distributions. Differences between ciliate assemblages were associated with water quality characteristics typical of urban stream degradation and may be related to factors such as nutrient availability and macroinvertebrate communities. Microscopic and molecular techniques were considered to be useful complementary approaches for investigation of biofilm ciliate communities.
纤毛虫是水生生态系统的重要组成部分，作为细菌和原生动物的捕食者，并为营养级更高的生物提供营养。然而，对于溪流生物膜中纤毛虫的多样性及其生态作用的了解仍然有限。本研究利用显微镜观察和基于18S rRNA序列的末端限制性片段长度多态性（T-RFLP）分析，评估了四条受人类活动影响程度不同的溪流生物膜样本中的纤毛虫多样性。对3'和5'末端片段的分析得出了非常相似的纤毛虫多样性估计值。显微镜观察检测到的多样性始终低于T-RFLP分析所显示的多样性，这表明存在形态学检查无法发现的遗传多样性。显微镜观察和T-RFLP分析揭示了不同溪流之间多样性的相似相对趋势，受影响最小的溪流样本中与生物膜相关的纤毛虫多样性水平最低，而中度至高度受影响的溪流样本中多样性最高。多变量分析提供了证据，表明不同溪流和季节的生物膜样本中纤毛虫群落存在显著差异，尤其是在高度退化的城市溪流和受影响较小的溪流之间。显微镜观察和T-RFLP数据均表明，存在广泛分布、适应性强的与生物膜相关的纤毛虫，以及仅限于特定环境条件地点的纤毛虫类群，其中世界性类群比分布受限的类群更为丰富。纤毛虫组合的差异与城市溪流退化典型的水质特征相关，可能与营养物质可用性和大型无脊椎动物群落等因素有关。显微镜观察和分子技术被认为是研究生物膜纤毛虫群落的有用互补方法。
